Our laboratory has demonstrated that the ability of the ch14.18 monoclonal antibody (MoAb) to mediate antibody-dependent cellular cytotoxicity (ADCC) is enhanced if the effector cells tested have first been activated with interleukin-2 (IL-2). Similarly, the cytotoxicity of in vivo activated lymphokine activated killer (LAK) cells can be augmented in vitro by the R24 antibody. We have also demonstrated that in vitro, more small cell carcinoma cells, neuroblastoma cells and melanoma cells bind MoAb when exposed to a combination of the ch14.18 antibody and R24 MoAb than when exposed to either MoAb alone. Therefore, based upon this preclinical data, our goals are to determine the tolerability and toxicity of a combination of ch14.18, R24, and IL-2 in patients with metastatic melanoma, soft tissue sarcomas, or extensive stage small cell carcinoma of the lung, or in patients whose tumor binds either the ch14.18 or R24 MoAb as demonstrated by immunohistochemical staining.